The ability of triamterene to control blood pressure, alter the renin-aldosterone axis and cause clinical and biochemical side effects is being assessed. In addition, because of the many undesirable side effects of spironolactone, triamterene is being evaluated as a suitable alternative potassium-sparing diuretic in the treatment of hypertension. Triamterene has been shown to be an effective antihypertensive agent in most patients with fewer side-effects, to date, then spironolactone. Further analysis needs to be done to correlate antihypertensive effect with renin status, and also to determine the mechanisms of fall in creatinine clearance and of polydipsia.